Smallpox can be considered the most deadly of all human infectious diseases, having killed hundreds of millions over the course of history. In 1980, smallpox became the only known human infectious disease to have been completely eradicated through a vaccination campaign conducted by the World Health Organization. However, illicit and surreptitious stocks of the virus pose a bioterrorism threat to the current population (Longini, et al. Int. J. Infec. Dis. 2007, 11, 98-108), the vast majority of whom have never been vaccinated due to its general discontinuance since 1980. In addition, the vaccine is contraindicated for the immune compromised segment of the population that has expanded in more recent times with the advent of AIDS and transplant recipients. In the event of a smallpox outbreak, the timing required to develop immunity by vaccination might not be sufficient for a large portion of the population. Therefore, effective therapeutics are needed to safeguard the largely immunologically naïve human population by providing immediate protection.